Suggestions for supplements to Layer Mix for breeders

I'm an amateur chicken growier who has a small flock of chickens for fun and eggs. I'd like to set some eggs, and was wondering about supplementing my girls' layer mix to ensure the best possible outcome. Does anybody have any suggestions? I am currently feeding a Layer Mix from our local elevator. I bed them down with alfalfa hay so I assume they get a little protein there. After reading through some posts, I'm going to get some BOSS. Is there anything else?

Thanks for your help. I really appreciate it. I do have a bunch of reference books, but we are living with my parents while we build a house and everything I own is in storage! (MY 4-year old recently asked if we could just move into our storage unit. He misses his stuff!)

After a few less that great hatches from my own eggs, I can say that I'm convinced my hens (and maybe the roo) weren't getting the right nutrients to create healthy chicks. Awesome eggs for the kitchen, definitely, but they didn't hatch well.

When I asked the same question a few weeks ago, the serious breeders who responded all said they feed their breeding flocks a higher protein feed rather than a standard layer feed. Since then I've been adding additional fish meal to my layer mash and making sure that they always have some in the supplement cup. I'll probably try hatching another dozen in the near future to see if I'm getting the results I want.